1. Field of the Invention
The present invention relates to an electrophotographic method using an amorphous silicon photosensitive material. More particularly, the invention relates to an electrophotographic method which enables the life of the photosensitive material to be lengthened without permitting image to flow and makes it possible to stably obtain image for extended periods of time.
2. Description of the Prior Art
An amorphous silicon photosensitive material has been extensively used for electrophotography. The amorphous silicon (a-Si) photosensitive material exhibits high sensitivity on the side of long wavelengths and further gives such advantages as excellent surface rigidity and abrasion resistance.
In the case of a copying machine using the amorphous silicon photosensitive material, however, the surface of the photosensitive material is oxidized and tends to absorb moisture after the photosensitive material is repetitively used. As a result, the surface resistance decreases, the surface charge migrates in the transverse direction and the image flows. To cope with this, it has been attempted to scrape off the oxidized portions on the photosensitive material surfaces and to exhaust ozone which is the cause of oxidation.
Japanese Laid-Open Patent Publication No. 15154/1986 discloses polishing an amorphous silicon photosensitive material by using, as a toner for the amorphous silicon photosensitive material, the one obtained by adding, to the surfaces of the toner, silicon carbide having an average particle diameter of from 0.1 to 1 .mu.m in an amount of from 0.005 to 5% by weight based on the toner.
Polishing the surface of the amorphous silicon photosensitive material Is surely effective in preventing the flow of image. However, there is no definite criterion in regard to what extent the surface be scraped off. When the surface is excessively polished, the charging performance is impaired and the life of the photosensitive material is shortened. When the amount of polishing is small, on the other hand, the image tends to flow making it difficult to stably form the image.
This problem similarly holds in exhausting ozone; i.e., excess of exhaust results in an increase in the cost of fans, energy cost, and cost of ozone-absorbing agent, and too weak exhaust permits image to flow.